We propose to study the structures, synthesis and functions of bacterial membrane lipids along the following lines: (1) Studies in vitro on the biosynthesis of plasmalogens in anaerobic bacteria. This pathway is distinct from that found in higher organisms. (2) Studies on the functions of plasmalogens in bacterial membranes. These will focus on: changes in the aldehyde chains as a function of growth temperature, changes in physical properties of the lipids and the membranes, effects of these changes on physiological properties of membranes. (3) Studies on the role of the acyl carrier protein (ACP) in complex lipid synthesis in bacteria. These will be concentrated mainly on the free ACP- dependent acylation of sn glycerol 3-p and on the regulation of phosphatidic acid formation of E. coli, C. butyricum and photosynthetic bacteria. (4) Studies on the positional isomer specificity of cyclopropane fatty acid & aldehyde synthesis in bacteria. Studies on the role of cyclopropane fatty acids - these will be mainly concerned with determining their protective effects, if any, under non-growing conditions. (5) Studies on the integration of outer membrane proteins into the outer membrane and the effects of alterations in lipopolysaccharide structure on this process.